Now to the gun control debate startg today on capitol hill leading to a vote possibly in the senate. The first lady made an unusual and tearful public plea for gun control and background checks on sales of guns just yesterday in chicago. Abc's jonathan karl has the latest in washington. Jonathan, this is the first we've seen her go in public policy, I think. Reporter: That's right, elizabeth. With the senate poised to take its first gun control vote in a decade later this morning, the first lady is clearly stepping into the fray. Something we rarely see from chelle obama. The first lady speaking in chicago making a direct appeal to congress on a hot political issue. The president's plan to combat gun violence. These reforms deserve a vote in congress. Reporter: Mrs. Obama choked back tears as she talked about attending the funeral of hadiya pendleton one week after her husband's inauguration. I told them that there is a reason we are here on this earth and I urge them to use their lives to give meaning. I urge them to dream as big as she did. Reporter: Overnight in washington victif gun violence include family members of some of those killed at sandy hook elementary read the names of every person killed since that dark day in december. Sandy hook families have been making the rounds on capitol hill imploring senators to pass new gun laws, a meet left one of the principal architects after a possible compromise in tears. I'm a parnent. I'm a grandparent. I can't -- I just can't. Let's all share. I can't imagine -- I just -- i can do something. Reporter: The emotional appeals come just as we are seeing the very first bipartisan agreement on guns in more than a decade. This coming -- this agreement to require background checks on all gun purchases at gun shows and online. George, as I said, the first bipartisan deal on guns we have seen in years. Debate begins today. Jon, thanks very much.

This transcript has been automatically generated and may not be 100% accurate.

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